In certain applications, in particular in the field of electronics, there is a need to provide circuits with ever-increasing performance, while taking up less and less space. This need tends to be satisfied by providing devices and electronic circuits based on innovative “packaging” architectures, combined with component stacking and assembling technologies and electrical interconnections. The main motivation results from a construction choice of the “packaging” that aims to achieve maximum electrical performance, accompanied by reduced encumbrance.
Generally, thin layer microelectronic components today still form the bridgehead in the development of electronics. Among the most studied devices, there are systems for storing energy such as micro-batteries with a lithium base, systems for recovering energy such as organic photovoltaic cells and organic photo-detectors or, also, systems for displaying such as organic light-emitting diodes.
The common problem of these circuits and of the active layers that they are comprised of, resides in their rapid degradation in the presence of oxidizing gases of the atmosphere, water and oxygen. These electronic components, for the vast majority, embed encapsulation solutions so as to avert the oxidizing and corrosive elements present in the surrounding atmosphere. With respect to barrier performance, the requirements can vary from one application to another. However, it is frequently admitted that the global level sought is between 10−4 and 10−6 g·m−2·j−1 for the Water Vapor Transmission Rate (WVTR) criterion and between 10−4 and 10−6 cm−3·m−2·j−1 for the Oxygen Transmission Rate (OTR) criterion.
The encapsulation solutions described in prior art can be divided into two families: encapsulating product and added case. The term encapsulating product means a sealed barrier system carried out monolithically on the stack of active layers of a microelectronics device. This solution refers to the hybrid multilayer structures that alternate organic thin layers with inorganic thin layers deposited by standard vacuum deposition technologies. The principle of an encapsulation by added case is generally based on the carrying out of a sealed cavity of which the atmosphere is controlled (vacuum, pressure, gas). This encapsulation, referred to as heterogeneous, is considered to be one of the most reliable solutions for meeting the needs of microelectronic devices sensitive to the air. The main motivations for this mode of encapsulation primarily reside in the ease of implementing it, its low cost and its performance (barrier, mechanics, adherence, thermal), in comparison with monolithic encapsulation solutions. In this technology, the encapsulation system can be produced separately before transferring it onto the support containing the active layers forming the microelectronic device. As such, the sealed cavity can be defined, for example, by a cover transferred and sealed onto a substrate containing active layers sensitive to the air. These solutions of transferring the cover adapt perfectly to the requirements of integrating microelectronic devices thanks in particular to their capacity of reducing their dimensions of length, width and thickness.
Whether they are monolithic or heterogeneous, the first function of the encapsulation solutions is to protect the microelectronic device from the external environment. However, these solutions must also offer easy integration via direct access to the input/output pads of the components.
In order to overcome this disadvantage, it has been proposed to use the technologies of “through-vias” machined in one of the substrates as described in EP A1 1557394, most often in the covers in order to access the electrical contacts. However the problem then arises of the seal and hermeticity of the vias constituted in relation to the oxidizing elements. In this case, the vulnerability of the encapsulation solutions via a cover depends exclusively on passages created in the cover or in the receiving substrate. The electrical connection for the purposes of a tapping can also be improved.
An object of this invention is to provide a method for producing and an encapsulation system that at least partially overcomes certain disadvantages of the existing methods.